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English
strcmp (string compare) is a built-in PHP function used to compare the size of two strings. It compares the strings character by character until a difference is found. If the two strings are identical, strcmp returns 0; if the first string is greater than the second, it returns a positive integer; if the first string is smaller, it returns a negative integer.
Syntax:
<span><span><span class="hljs-title function_ invoke__">strcmp</span></span><span>(</span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$str1</span></span><span>, </span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$str2</span></span><span>): </span><span><span class="hljs-keyword">int</span></span><span>
</span></span>Parameters:
$str1: The first string to compare.
$str2: The second string to compare.
Return Values:
Returns 0 if the two strings are equal.
Returns a negative number if $str1 is less than $str2.
Returns a positive number if $str1 is greater than $str2.
Example:
<span><span><span class="hljs-variable">$str1</span></span><span> = </span><span><span class="hljs-string">"apple"</span></span><span>;
</span><span><span class="hljs-variable">$str2</span></span><span> = </span><span><span class="hljs-string">"banana"</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-title function_ invoke__">strcmp</span></span><span>(</span><span><span class="hljs-variable">$str1</span></span>, </span><span><span class="hljs-variable">$str2</span></span><span>); </span><span><span class="hljs-comment">// Outputs a negative number because "apple" < "banana"</span></span><span>
</span></span>strcmp is case-sensitive, meaning that two strings with the same letters but different cases are considered different.
Similar to strcmp, strcasecmp (string compare, case-insensitive) is also used to compare two strings. The difference is that strcasecmp ignores case when comparing strings. This makes it more flexible, especially when case-insensitive comparisons are needed.
Syntax:
<span><span><span class="hljs-title function_ invoke__">strcasecmp</span></span><span>(</span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$str1</span></span><span>, </span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$str2</span></span><span>): </span><span><span class="hljs-keyword">int</span></span><span>
</span></span>Parameters:
$str1: The first string to compare.
$str2: The second string to compare.
Return Values:
Returns 0 if the two strings are equal (case-insensitive).
Returns a negative number if $str1 is less than $str2.
Returns a positive number if $str1 is greater than $str2.
Example:
<span><span><span class="hljs-variable">$str1</span></span><span> = </span><span><span class="hljs-string">"apple"</span></span><span>;
</span><span><span class="hljs-variable">$str2</span></span><span> = </span><span><span class="hljs-string">"APPLE"</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-title function_ invoke__">strcasecmp</span></span><span>(</span><span><span class="hljs-variable">$str1</span></span>, </span><span><span class="hljs-variable">$str2</span></span><span>); </span><span><span class="hljs-comment">// Outputs 0 because "apple" and "APPLE" are equal when case is ignored</span></span><span>
</span></span>The core difference between strcmp and strcasecmp is whether they are case-sensitive:
strcmp is case-sensitive and considers letter case as part of the comparison.
strcasecmp is case-insensitive and treats letters with different cases as equivalent.
Use strcmp when you need to strictly compare strings according to case.
For example, in a file system where filenames are case-sensitive, especially on case-sensitive operating systems like Linux.
Use strcasecmp when you want to ignore letter case during comparison.
For example, when processing user input where case may vary but you want the comparison to be case-insensitive.
Example:
<span><span><span class="hljs-variable">$usernameInput</span></span><span> = </span><span><span class="hljs-string">"Admin"</span></span><span>;
</span><span><span class="hljs-variable">$usernameDatabase</span></span><span> = </span><span><span class="hljs-string">"admin"</span></span><span>;
<p></span>if (strcasecmp($usernameInput, $usernameDatabase) === 0) {<br>
echo "Username matches!";<br>
} else {<br>
echo "Username does not match!";<br>
}<br>
</span>In this example, strcasecmp is used to compare the username entered by the user with the username in the database. Regardless of whether the letters are uppercase or lowercase, they are treated as identical.
strcmp and strcasecmp are both functions for comparing two strings, but their main difference lies in case sensitivity. strcmp strictly considers letter case during comparison, while strcasecmp ignores case. Choose the appropriate function according to your needs to ensure correct comparison results. When dealing with sensitive data, case differences usually matter, whereas for user input or non-sensitive data, case-insensitive comparison is often more convenient.
